In recent years, there has been a general trend towards reduced size and increased mobility for many types of consumer equipment. For example, the use of portable phones, computers, personal music systems and personal digital Assistants (PDAs) have become increasingly widespread.
The market for handheld and portable consumer electronics and computing has significantly diversified in the last decade. The trend has increasingly been towards smaller devices capable of displaying increasing amounts of information leading to improved displays having higher resolutions.
In addition, the user interface has progressed significantly and much effort has been put into providing an intuitive interaction mechanism. A frequently used method for receiving user inputs is by incorporating a touch screen in the device. This allows for a user interaction by the user touching a touch sensitive display.
Conventionally, the touch sensitive display is formed by a transparent touchscreen being placed on top of a display element. The touch screen will thus face the user and when pressed by the user, the device may detect the location of the pressure point and operate in response to this detection. Thus, the touchscreen device will identify the coordinates of the point being pressed whereby the device can determine and perform the selected actions.
However conventional touch sensitive displays are not able to detect a plurality of touches because each signal obtained from each touched location flows in the same electrodes with the signals not being distinguishable. As a result, the signals overlap and only superposition of all the generated signals can be detected.
Furthermore, conventional touch sensitive displays are expensive and tend to be complicated to manufacture. Additionally, they tend to be mechanically sensitive and prone to mechanical failures. Also, conventional touch sensitive displays typically have a touchscreen placed on top of the display element and is therefore placed between the user and the display element. This degrades the optical performance of the touch sensitive display and requires that materials having suitable optical properties are used to implement the touchscreen.
Additionally, conventional displays tend to comprise a large number of layers resulting in a significant thickness of the resulting touch sensitive display. A further disadvantage with many conventional displays is that they require careful calibration in order to provide accurate position detection and especially to provide accurate position detection relative to an image displayed on the touch sensitive display.
Hence, an improved touch sensitive display would be advantageous and, in particular, a touch sensitive display allowing for improved mechanical reliability, reduced cost, reduced complexity of manufacturing, reduced thickness, reduced calibration requirements and improved optical performance